Apparatus for silencing pulsating gases



May 6, 1941. A. s. CHIPLEY APPARATUS FOR SILENCING PULSATING GASES Filed Dec. :50. 1938 2 Sheets-Shet 1 w w/ o 06 0 A 9 we 6 Q6 x f 9 a o [w o 4 OH 90 9 W MM M o 0e y e 0 6 0 f oo o co e 90 M o y 90 o 90 1 o f 96/ 0 0e e 9.0 i

May 6, 1941. A. s. CHIPLEY APPARATUS FOR SILENGiNG PULSATING GASES 7 Filed Dec. 30, 1938 2 Sheets-Sheet 2 I fiaezz/ar: /fd j (Zy'J/e W M Patented May 6, 1941 2,241,010 APPARATUS FOR smancmo. PULSATING GASES Alfred S. Chipley, Chicago, 111.,

assignments, to Burgess Battery assignor, by mesne Company, Ohicago, 111., a corporation of Delaware Application December 30, 1938, Serial No. 248,485

8 Claims.

This invention relates to improvements in apparatus for silencing pulsating flowing gas streams, and particularly to silencers for the inintroduced into a chamber and there allowed to expand into substantially the entire volume of the chamber, after which they pass out of the chamber through an open-ended, perforated outlet conduit whichextends into the chamber from the outlet opening to a point adjacent the opposite wall of the chamber. The outlet conduit leads into a second expansion chamber where the action is repeated.

Silencers employing a single expansion chamber have been used heretofore but such a chamber is not adequate to meet the silencing requirements demanded at the present time. To meet the deficiency, supplementary silencing constructions have been used in some cases. An expansion chamber is a simple and economical construction, however, and in accordance with this invention it has been discovered that full use may be made of its advantages. 'It has been discovered that the addition of ,a second chamber of the type describedbriefiy above produces unexpected and surprising results in that it produces a pronounced increase in effectiveness so as to silence the entire range of frequencies normally encountered and effect completely adequate silencing, while producing only a slightincrease in the resistance to gas flow. These performance characteristics will be explained more fully hereinafter.

In the drawings,

,Figs. 1, 2, 3, 4, 5, 6 and 8 are longitudinal sectional views of different modifications, of the silencer of this invention; and

Figs. 7 and 9 are transverse sectional views along lines lel and 9-9 of Figs. 6 and 8, respectively. 1

The construction of Fig. 1 comprises a substantially imperforate casing 10 having inlet and outlet end walls II and I2, these end walls having inlet and outlet openings I3 and 14 therein respectively. A partition 15 extends across the casing and subdivides it into two expansion chambers 16 and I1. Partition 15 has an open ing l8 therein arranged in offset relation with respect to inlet and outlet openings 13 and 14, that is, it is displaced laterally a substantial distance out of alignment with said inlet and outlet openings. A perforated, open-ended outlet tube I9 is mounted at one end thereof in opening 18 [of partition l5 and extends forwardly into the first expansion chamber Hi to a point adjacent the opposite inlet end wall H. The dimensions of this tube and the distance it extends into chamber l6 are not critical, but it should be an elongated tube in which the length is equal to at least twice the diameter, and it should extend into the chamber a distance equal to at least twice its diameter. A perforated, open-ended outlet tube 20 is mounted at one end in outlet opening I4 of the second chamber 11 and extends forwardly in said chamber to a point adjacent the inlet end wall of the chamber, which is partition l5. An inlet snout is connected to inlet opening 13 of the silencer, and an outlet snout 22 is connected to outlet opening 14, this snout being a continuation of outlet tube 20. The snouts 2| and 22 are used to connect the silencer in the exhaust or intake system.

When the device is used for silencing the exhaust gases of an internal combustion engine, inlet snout 2| is connected to the exhaust pipe of the engine. In operatiomthe exhaust consists of a series of high pressure gas pulsations, usually called slugs, traveling at high velocity and separated from one another by areas of low pressure, which may be lower than atmospheric pressure. The gases pass through inlet opening 13 and emerge into the first expansion chamber 16. Here they are free to expand into substantially the entire volume of the chamber, and they become cooled and contracted and their kinetic energy is reduced substantially. Some of the gases pass laterally directly from chamber l6 through the perforations of outlet tube 19 and into said tube, while the remainder pass rearwardly to the opposite wall 15 of the chamber, reverse their direction and pass forwardly to the forward end and then reverse their direction again and pass into the open end of outlet tube 19 and through this tube into the second expansion chamber I1.

The pulsations of the gases entering the second chamber H are modified substantially. The pressure and velocity thereof are reduced considerably. They are free to expand again into substantially the entire volume of chamber 11' and undergo in that chamber an actionslmilar to" that described in connection with the first chamber l6. There is such a pronounced reduction in the velocity and pressure of the pulsations within chamber l1 whereby the rise and fall of pressure of the emerging gases are only gentle and are incapable of producing any sharp, objectionable noises, and the gases leaving the chamber are substantially completely silenced, making at most a soft puffing noise which is not objectionable, and, in fact, is barely audible. As stated heretofore, the second expansion chamber, while contributing a pronounced silencing efiect, contributes only slightly additional resistance to flow. In a specific application of a silencer to a single cylinder, 4 cycle, 2 horsepower internal combustion engine, having a 1 inch diameter exhaust pipe, a silencer 7 inches long and consisting of a single expansion chamber similar to the chambers of Fig. 1 was first applied. The silencing was noticeable over the noise created by the engine without any silencer, but was considerably less than what would be satisfactory for commercial use, and the back pressure at the engine exhaust was 4 /2 inches of water. The substitution of a silencer 14 inches long and consisting of two chambers, as is shown in Fig. 1, produced a pronounced increase in the silencing efiect such that the silencing was entirely satisfactory for commercial use. The back pressure at the engine exhaust was 6 inches of water, an increase of only 1 inches of water over the single chamber. Such were the conditions without a tail pipe attached to the outlet of the silencer, and when a tail pipe 4 feet long was attached to the outlet of the single chamber silencer the back pressure at the engine exhaust was 9 inches of water, and when the same tail pipe was attached to the end of the double chamber silencer, it was inches of water. This difference of back pressure is, of course, important because silencers are usually used with tail pipes. The difference is probably due to the pronounced smoothing effect upon the pulsations in the second chamber. It is to be noted that, withthe double chamber silencer the back pressure is slightly lower when the tail pipe is present than when it is absent. This may be because there is a steady column of gas passing at relatively low velocity through the tail pipe which may act to draw the gas from the engine. The pulsations in the tail pipe following the single chamber silencer may not have such an effect. Although the reasons for it are not clearly understood, the back pressures obtained in the presence of a double chamber silencer are surprisingly low.

The double chamber silencer described possesses properties of efiectiveness which are interesting and peculiar. For example, if the outlet tubes for the expansion chambers have solid,

instead of perforated, walls the device does not provide satisfactory silencing. It is highly effective at some frequencies, or engine speeds, while at others it effectiveness is low, so that at these speeds it produces an objectionable noise, in the nature of a roar. ance action set up by the solid tubes which is This may be due to a resonlencing is obtained for satisfactory performance.

In Fig. 2 is illustrated a modification of the structure of Fig. 1 in which the outlet tubes are closed at their inlet ends. The device comprises a substantially imperforate casing 25, having a partition 26 dividing itinto two expansion chambers 21 and 28, these expansion chambers having inlet openings 29 and 30, and perforated outlet tubes II and 32, outlet tubes being arranged in offset relation with respect to the inlet opening in each chamber. The outlet tubes are closed at their inlet ends 33 and 34 and all of the gases pass into these tubes through the openings in the walls thereof.

In F18. 3 a modification of the structure is shown in which the inlet snouts of the chambers project into the chambers a short distance and the outlet tubes have elongated slots, instead of small openings, in the walls thereof. The device comprises a substantially imperforate casing 40 divided into two chambers 4i and 2 by partition 43. Inlet snout passes through opening 45 of chamber 4| and projects into the first chamber H a short distance. Open-ended. outlet tube 46 extends into chamber 4|, this tube and the inlet snout 44 being arranged in substantially non-overlapping relation. If there is a substantial overlapping, the resistance to flow offered within chamber ll is increased. By this it is not meant that such back pressure would be excessive for silencers of this general character. but since the improvement of this invention has low back pressure for one of its primary advantages, it is preferred to avoid any substantial overlapping of the tubes.

Outlet tube 48 for chamber 4| extends a short distance into the second chamber "to form an inlet snout 41 for said chamber. Instead of having small openings in its wall, the outlet tubes have elongated slots 49 therein. The operation of this modification is substantially similar to that described heretofore in connection with Fig. 1 except that the gases passing through the walls of the outlet tubes follow a somewhat different Path, passing through the slots instead of the small openings.

in Fig. 4 a modification is'illustrated in which there are several outlet tubes for the first chambet and inlet openings for the second chamber. The device comprises a substantially imperforate casing I having substantially axial inlet and outlet openings Ii and 52. A partition 53 divides'the easing into two chambers 54 and 5!. Partition II has two openings 58 and 51 therein, both being offset with respect to the inlet and outlet openings BI and -52. Tubes 58 and 59 are mounted in openings 56 and 51 respectively,

, and extend into the first expansion chamber 54.

prevented when openings are provided in the' tube walls. If a single chamber silencer is substituted for the two-chamber device, this single chamber having the same size and dimensions as the casing oi the two-chamber device, the silencing is not better than that produced by a single small chamber, such as chamber It. Further, if the device shown in Fig. 1 is turned end-for-end, so that the gases pass through it in a direction opposite to that described above, insufficient si- The tubes II and SI are of smaller diameter than the inlet and outlet openings 5| and 52, the total cross sectional area of the tubes, however, being at least as great as the area of the inlet and outlet openings. An open-ended perforated outlet tube II is mounted in outlet opening 52 and extends into the second expansion chamber [5. The gases enter the silencer through inlet opening ii where they expand into substantially the entire volume of chamber 54 and then pass into tubes 58 and." in substantially the same manner as described in connection with the passage oi gases from, the inlet to the outlet tube of the silencer of Fig. 1, except that instead of passing laterally from one side to the other of the gases are again free to expand. and they converge and collect in tube 60 and pass out of said tube in a stream of gently rising and falling pulsations. The construction illustrates the general principle that a number of inlet openings and outlet tubes may be provided for the chambers. While two are shown in this modification, the number may be increased as desired. As the number is increased, the diameters should be correspondingly decreased so as to avoid the too.

ready fiow of gases through the chambers and the sacrifice of silencing which would result.

In Fig. 5 a modification is illustrated in which the gases leave the silencer in the opposite direction from that in which they enter. The device comprises a substantially imperforate casing 65 divided into two chambers 66 and 61 by a partition 68 which extends in what may be considered the longitudinal direction rather than the transverse direction. The inlet opening 69 for the first chamber 66 is in the same casing wall as the outlet opening 10 for the second chamber 61. A perforated, open-ended outlet tube H for the first chamber 66 is mounted in opening 12 in partition 68, which opening is located adjacent the inlet end of chamber 66.

Tube 1| extends transversely with respect to the inlet opening 69. A perforated outlet tube 13 for the second chamber 61 extends longitudinally rearward into said chamber in a direction proportion enters outlet tube 81 through the perforations thereof than does in the form of construction of Fig. 1. As a result the silencing effectiveness is increased, and this is done at the expense of substantially no increase in resistance to fiow. it relatively small portion of the gases swerve laterally from inlet opening 84 and enter the open end of outlet tube 81. The action within the second expansion chamber 82 is substantially the same as that within the first.

In Figs. 8 and 9 a modification is shown in which the conduits extending into the chambers are not in the form of tubes, but are formed by arranging a perforated plate adjacent the wall of the casing to provide a space between the plate and wall, which space serves as a conduit. An opening in the outlet wall of each chamber is arranged to coincide with this space whereby the gases may pass out of the respective chambers. The device comprises substantially imperforate casing 95 which has a transverse partition 96 subdividing the interior into chambers '91 and 88. An inlet opening 99 is provided for the first chamber 91. An opening I00 is provided in partition 96 in offset relation to inlet opening 99, and a perforated plate IOI is joined to partition 96 at the edge of said opening and extends forwardly into chamber 91, its side edges being joined to the wall of the casing to form an outlet conduit III2 for chamber 91, This conduit in cross-section is in the shape of a segment of a circle, In chamber 98 a perforated plate I03 extends inwardly in a similar manner from the outlet opening I84 and forms an outlet conduit I05 with the opposite portion of the side wall of the casing 95. The action within this silencer is substantially the same as that which takes place within the other modifications, the gases and where it is desired to prevent rain, etc., from I entering the system, particularly during periods of inactivity.

In Figs. 6 and '7 a modification is illustrated in which a flange member surrounds the inlet end of each of the perforated outlet conduits and extends across a portion of the chamber occupied by such conduit. comprises substantially imperforate casing 86 which is subdivided into two expansion chambers 8I and 82 by a transverse partition 83. The casing has inlet and outlet openings 84 and 85 arranged eccentrically in the inlet and outlet end walls thereof. These openings may be in alignment with each other, and partition 83 has an opening 86 therein arranged eccentrically thereof and offset with respect to openings 84 and 85. Open-ended perforated outlet tubes 81 and 88 are mounted at one end in openings 86 and 85, and extend into chambers 8| and 82, respectively, and end in adjacent spaced relation to the forward walls of said chambers.. Substantially semi-circular flanges. 89 and 96 are mounted upon the forward ends of tubes 81 and 88 and are joined to the adjacent surfaces of the casing wall.

In the operation of this modification, the exhaust gases enter the device by way of inlet opening 84 and the major portion is projected into the space rearwardly of flange 89. The return of the gases to the forward end of the chamber adjacent the open end of outlet tube 81 is impeded by flange 89 whereby a larger The construction following a slightly different path into the outlet conduits because only a portion of the walls thereof are perforated.

While the area occupied by the perforations of the outlet conduits of this invention is not critical, it has been found that this should be such that the entrance opening area into the conduits, including the ends of the open-ended conduits is from 1.5 to 6 times the area of the outlet openings of the chambers. Within this range, the perforated area may be varied to obtain the best silencing results for the particular engine, blower, air compressor, etc., to which the silencer is to be applied. With the construction of Fig. 2 the proportion of the area of the conduit walls occupied by the perforations may be somewhat greater than with that of Fig. 1

to compensate for the fact that the inlet ends are closed instead of open. Likewise, with the construction of Figs. 8 and 9 the proportion of the area of plates IOI and I 03 occupied by the perforations is somewhat greater, to compensate for the fact that only a portion of the conduit wall is perforated. The small openings may be replaced by larger openings of any desired shape and the terms perforations and perforated in the description and claims are intended to cover openings of any shape and size including slots. The openings should not be concentrated near the inletend of the conduit. Some should be located near the outlet end, and for best results should be distributed over the length of the conduits.

In the constructions illustrated, the two chambers are of the same size. They may be of different size, if desired, in which case the second chamber is usually smaller than the first because the gases undergo cooling and contraction in the first.

While the modifications described herein all have two chambers, and that number is adequate for the purpose, the invention is not limited in this respect and the use of additional chambers is within the scope of the invention.

I claim: 1. Apparatus for silencing noise-producing gases comprising a plurality of chambers, each chamber having an inlet opening in a wall thereof and an outlet conduit extending thereinto from the opposite wall thereof, said outlet conduit being arranged in non-aligned relation with the inlet opening. said outlet conduits having one or more gas entrance openings in the walls thereof and extending a substantial distance into said chambers respectively, the inlet opening and the openings the outlet conduit within each chamber being in substantially immediate communication with substantially the entire volume of said chamber, the outlet conduit of one chamber being connected to the inlet opening of another for the passage of gases through said chambers in succession.

2. The silencer of claim 1 in which the area occupied by the gas entrance openings of the outlet conduits is approximately 1.5 to 6 times the area of the chamber outlet openings to which said conduits are connected.

3. Apparatus for silencing noise-producing gases comprising a plurality of chambers, said chambers each having inlet and outlet openings in opposite walls thereof, an outlet conduit communicating with the outlet opening of each of said chambers, the outlet conduit being arranged in non-aligned relation to the inlet opening within each chamber and extending a substantial distance into said chamber, said outlet conduits having gas entrance openings in the walls and the ends thereof, the area occupied by the gas entrance openings of the outlet conduit within each chamber being approximately 1.5 to 6.0 times the area of the outlet opening of said chamber, the inlet opening and the gas entrance openings of the outlet conduit within each chamber being in substantially immediate communication with substantially the entire volume of said chamber, the outlet conduit of one chamber being connected to the inlet opening of another for the passage of gases through said chambers in succession.

4. Apparatus for silencing noise-producing gases comprising a plurality of chambers, said chambers each having inlet and outlet openings in opposite walls thereof, an outlet conduit communicating with the outlet opening of each of said chambers, the outlet conduit being arranged in non-aligned relation to the inlet opening within each chamber and extending toward the opposite wall of said chamber, said outlet conduits having one or more openings in the walls thereof, the inlet opening and the openings of the outlet conduit within each chamber being in substantially immediate communication with substantially the entire volume of said chamber, at least one of said outlet conduits having a flange member projecting laterally outward adjacent the inlet end thereof, the outlet conduit of one chamber being connected to the inlet opening of another for the passage of gases through said chambers in succession.

5. Apparatus for silencing noise-producing gases comprising two chambers, said chambers each having inlet and outlet end walls in opposite ends thereof, said end walls having inlet and outlet openings therein, the inlet and outlet openings of each chamber being in non-aligned relation to each other, an open-ended perforated conduit mounted in the outlet opening in each of said chambers and extending into said chamber part way toward the inlet end wall of said chamber, the inlet opening and the outlet conduit within each said chamber being in substantially immediate communication with substantially the entire volume of said chamber, the outlet conduit of the first of said chambers communicating with the inlet opening with the second of said chambers.

6. Apparatus for silencing noise-producing gases comprising a plurality of chambers, said chambers having inlet and outlet openings in opposite walls thereof, a perforated conduit mounted in the outlet opening of each chamber, the outlet conduit of each chamber being arranged in non-aligned relation to the inlet opening of said chamber and extending into said chamber a distance equal to at least twice the diameter of said conduit, the inlet opening and the perforations of the outlet conduit within each chamber being in substantially immediate communication with substantially the entire volume of said chamber, said chambers being connected together for the passage of gases therethrough in succession.

'7. The silencer of claim 1 in which the outlet conduit in each chamber has a multiplicity of small openings in the walls thereof.

8. The silencer of claim 1 in which there is a short snout extending into each chamber from the inlet opening thereof, said snout being in non-overlapping relation with the outlet conduit.

ALFRED S. CHIPLE'Y. 

